In general, optical products provide clearly-reflected images such as goest and flare, but do not provide clear visibility. Accordingly, an anti-reflective layer is formed on a substrate in order to acquire the clearly-reflected image and the clear visibility. The anti-reflective layer is generally made of silicon oxide or magnesium fluoride having high hardness and a low refractive index.
However, when the optical products, of which the anti-reflective layer made of silicon oxide or magnesium fluoride is included on the surface, are cleaned with water but not sufficiently wiped and left as it is for drying, the anti-reflective layer is stained with spots such as water left on the surface, so called a “water stain” and as a result, visibility is deteriorated. In order to prevent the spot, water repellent processing may be performed on the surface of anti-reflective layer with curable polysiloxane, a silane compound having a water repellent property, and the like.
As described above, the optical product having both anti-reflection and water repellency is generally manufactured by coating a refractive index matching material for an anti-reflective property and coating a water repellent material for a water repellent property, on a flat base.
However, in order to acquire both the anti-reflective property and the water repellent property, a plurality of thin film layers having the anti-reflective property and the water repellent property need to be repetitively coated and although the water repellent material is coated on the anti-reflective layer, it is difficult to acquire a substrate having a contact angle of 120° or more. Further, in order to reduce reflection in a wide wavelength area, a multi-coating method which performs anti-reflective coating several times needs to be used, but this is an important factor of increase in a product cost due to increase in a coating cost.